MSD 8566 Installation
MSD Pro-Billet V8 Distributor
Buick 400, 430, 455, PN 8517
Buick 215, 300, 340, 350, PN 8548
Oldsmobile, PN 8566
Pontiac, PN 8563
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Important: Read these instructions before attempting the installation.
Note: An MSD Ignition is required with this Distributor.
Parts Includ e d:
1 - Pro-Billet Distributor
1 - Rotor, PN 8467
1 - Distributor Cap, PN 8433
1 - Wire Retainer
2 - 1.5" Self Tapping Screws
2 - 10-32 x 3/4" Socket Head Screws
WARNING: Before installing the MSD Distributor, disconnect the battery cables. When disconnect-
ing the battery cables, always remove the Negative (-) cable first and install it last.
1 - Advance Kit
1 - Gasket (Pontiac, Olds Only)
1 - Tube of Gear Lubricant
1 - O-Ring (Buick Only)
Note: The terminals of this Distributor Cap require spark plug style terminals. You may need to change
the terminals and boots of your wires. MSD offers two kits, PN 8849 or PN 8848 that are supplied
with nine boots and terminals.
Note: If you prefer the GM socket style cap, MSD offers one as PN 8437.
TIMING FUNCTIONS
Before continuing with the installation, here are a few definitions you should be aware of:
Initial Timing: This is the base timing (also referred to as idle timing) of the engine before the centrifugal
advance begins.
Centrifugal Advance: The centrifugal (or mechanical) advance mechanism is made up of weights,
springs, advance cams, and an advance stop bushing. The amount and rate of advance that your
distributor is capable of is determined by the centrifugal timing. If you ever wish to lock out the
centrifugal advance, refer to the centrifugal advance section.
Total Timing: This is the total of the initial timing plus the centrifugal advance added together. Example:
10° Initial + 25° centrifugal = 35° Total Timing.
Note: MSD Distributors are supplied with the heavy (slow) advance springs installed. This is to prevent
detonation in certain applications. Review the information on pages 2-4 to determine the best
advance curve for your application.
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2 INSTALLATION INSTRUCTIONS
CHOOSING AN ADVANCE CURVE
The function of the advance curve is to match the ignition timing to the burning rate of the fuel and
speed (rpm) of the engine. Any factor that changes the burning rate of the fuel or the engine speed
can cause a need for an ignition timing change. Figure 1 shows some of the factors that will affect
engine timing.
FACTOR Advance Timing Retard Timing
For For
Cylinder Pressure Low High
Vacuum High Low
Energy of Ignition Low High
Fuel Octane High Low
Mixture (Air/Fuel) Rich Lean
Temperature Cool Hot
Combustion Chamber Shape Open Compact
Spark Plug Location Offset Center
Combustion Turbulence Low High
Load Light Heavy
Figure 1 Ignition Timing Factors.
As you can see from the chart, most factors will change throughout the range of the engine operation.
The timing mechanism of the distributor must make timing changes based on these factors.
Example: An engine has 11:1 compression with a high energy ignition. With the specifications given,
you will have to retard the timing for the high compression and high energy ignition. By comparing
the engine’s specifications against the chart, a usable timing guideline can be found. Engines with a
combination of items from both columns will require a timing that is set in the mid range.
Obviously a full technical explanation of correct ignition timing would be very complicated. The best
way to arrive at a suitable ignition curve for your engine is to use the Ignition Timing Factors Chart
as a guide and compare it to the Advance Graphs in Figure 4 until a suitable curve is found. When
selecting your advance curve, use detonation (engine ping) as an indicator of too much advance,
and a decrease in power as an indicator of too little advance.
TIPS ON SELECTING AN ADVANCE CURVE
• Use as much initial advance as possible without encountering excessive starter load.
• Start the centrifugal advance just above the idle rpm.
• The starting point of the centrifugal advance curve is controlled by the installed length and tension
of the spring.
• How quickly the centrifugal advance (slope) comes in is controlled by the spring stiffness. The
stiffer the spring, the slower the advance curve.
• The amount of advance is controlled by the advance bushing. The bigger the bushing, the smaller
the amount of advance.
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INSTALLATION INSTRUCTIONS 3
CENTRIFUGAL ADVANCE CURVE
SELECTING THE ADVANCE SPRINGS
The rate, or how quick the advance comes in
is determined by the type of springs which are
installed on the distributor. The MSD distributors
are equipped with two Heavy Silver s prings
installed. These will give you the slowest advance
curve possible (Figure 2). The parts kit contains
two additional sets of springs which can be used
to match the advance curve to your particular
application. Refer to the Spring Combination Chart
(Figure 3) for combinations that can be achieved.
To change the springs, remove the cap and rotor
and use needlenose pliers to remove the springs.
Be sure the new springs seat in the groove on
the pin.
Timing Curve From Factory
Figure 2 The Factory Equipped Curve.
SPRING COMBINATION RATE OF ADVANCE FIGURE 4
2- Heavy Silver SLOWEST A
1- Heavy Silver B
1- Light Blue
1-Heavy Silver C
1-Light Silver
2- Light Blue D
1- Light Silver E
1- Light Blue
2- Light Silver FASTEST F
Figure 3 Spring Combination Chart.
Figure 4 Advance Curves.
SELECTING THE ADVANCE STOP BUSHING
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